What are the pros and cons of a Tube Mic?

[Farview]

How right you are, but the M149 is a $4k mic and Neumann tests all tubes, out of 100 tubes the use only the best. The 6111 is a very small militairy tube that can be bought for $6.75. But when Neumann replaces the tube it'll cost $400+

Maybe you'll be in the position to buy a vintage U47 some day and some other day you have to replace the VF14 tube that's in there. I'm afraid you'll need much more than $400 then. ($1400 perhaps)

I'm just trying to stay on topic here, I have replaced tubes that have cost me a small furtune. I'm also a big fan of NOS tubes in my guitar amps. But we are talking about a Rode here. It was designed around a $10 12ax7.

 

[Marik]

I don't really see a good reason to put a Telefunken or Mullard into K2 for number of reasons.
First, as most tube mics it has a transformer, which is not the very best quality one, so without transformer replacement it is fruitless. Yes, you might hear some improvement... little bit... may be, but transformer (as a bad cable) will absorb most of it.
Second, I strongly believe 12AX7 is not a good tube for mic use, at all. The reason many modern manufacturers use it, is plain simple--low cost, and availability. The only suitable tube of 12__7 family for use in microphone would be 6072. GE 5 star would be one of the best. It is not very expensive and can be used instead of 12AX7 directly.